Substantial attention has been devoted to the development of electric power cells which employ a gas as one member and a chemically active solid state material as the other member of the electrochemical couple. One such type is a cell in which the anode is a chemically oxidizable metal and the depolarizer is oxygen, e.g. zinc/air and cadmium/air batteries. A second type utilizes an electrochemically reducible metal oxide, e.g. nickel oxide, at the cathode and a gas that is oxidizable and ionizable, e.g. hydrogen, at the anode. A cell of the latter type is disclosed in U.S. Pat. No. 3,544,375, issued Dec. 1, 1970 to Samuel Ruben for Rechargeable Fuel Cell.
The present invention also employs a reducible metal oxide cathode and an oxidizable and ionizable gas as the anodic agent. The primary object of the invention is to provide a battery that comprises two or more rechargeable cells that overcome certain of the limitations yet offer substantially all of the advantages of the cell disclosed by the aforesaid Ruben patent. More particularly, the cells employed in this invention avoid the requirements set forth in the Ruben patent of supplying hydrogen gas during discharge, venting hydrogen gas during recharging, and submerging the cell electrodes in the electrolyte. Another object of the invention is to provide a battery of the character described which can be repeatedly charged and discharged without need to add more oxidizable gas to the cell to sustain operation. A further object is to provide a battery of the character described that can operate over a wide range of ambient temperatures, has a relatively high energy density, and can be constructed in various configurations. yet another important object is to provide an electric battery having inherent overcharge and overdischarge protection and whose capacity or state of charge can be determined by measuring the gas pressure within the battery case. A further object is to provide a battery comprising a selected number of cells with the electrodes of two or more cells being disposed in a common battery case compartment.